The present invention relates generally to gas turbines, and more particularly to a gas-path leakage seal for a gas turbine.
Gas turbines include, but are not limited to, gas turbine power generation equipment and gas turbine aircraft engines. A gas turbine has a gas path which typically includes, in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). Gas leakage, either out of the gas path or into the gas path, from an area of higher pressure to an area of lower pressure is generally undesirable. For example, gas-path leakage in the turbine area of a gas turbine will lower the efficiency of the gas turbine leading to increased fuel costs. Also, gas-path leakage in the combustor area of a gas turbine will require an increase in burn temperature to maintain power level, such increased burn temperature leading to increased pollution, such as increased NOx and CO production.
Gas-path leakage occurs through gaps between gas turbine subassemblies such as through gaps between the combustor and the turbine, and gas-path leakage occurs through gaps between the components that make up a gas turbine subassembly, such as through gaps between combustor casing segments. Such components and subassemblies have surfaces of different shapes, suffer from assembly misalignment, and undergo vibration. Hot-section components thermally experience hot gas flow and typically undergo different thermal growths. Conventional seals are used to reduce such leakage. For example, a conventional rigid or leaf seal made of metal may have a leakage of 2.4% (primarily from flow around the seal due to different surface shapes, assembly misalignment, vibration, thermal growth, and/or wear). Such leakage in the combustor may result in a 15 (or much higher) parts-per-million (ppm) NOx production and a similar CO production. What is needed is an improved gas-path leakage seal for a gas turbine which will further increase efficiency and further decrease pollution, such as further decreasing NOx and CO production.